1. Field of the Invention
The present invention relates to a piezoelectric transducer using a piezoelectric element, and more particularly to an electrophoretic ink display apparatus using a piezoelectric transducer.
2. Description of the Related Art
The technology noted in Japanese Patent Laid-open Publication No.(Hei)8-125247 and Japanese Patent Laid-open Publication No.(Hei)9-162456 relates to conventional piezoelectric transducers. The embodiments therein are different, but both include technology using bulk piezoelectric ceramics.
Meanwhile, the paper in SID 98 Digest pp. 1131 to 1134 makes note of conventional electrophoretic ink display apparatuses. The constitution of a segment type display body using electrophoretic ink is disclosed in this paper.
In this electrophoretic ink display apparatus, each segment of the display apparatus is constituted of a plurality of microcapsules using electrophoresis. This is so that the color of a segment changes when voltage is applied to that segment.
However, the abovementioned background art has the following problems.
In the piezoelectric transducers noted in Japanese Patent Laid-open Publication No.(Hei)8-125247 and Japanese Patent Laid-open Publication No.(Hei)9-162456, bulk piezoelectric ceramics are used although the embodiments are different, as discussed above. It is difficult to miniaturize a piezoelectric transducer wherein bulk piezoelectric ceramics are used. For example, the piezoelectric transducer in Japanese Patent Laid-open Publication No. 9-162456 is 40 mmxc3x9710 mmxc3x971.5 mm.
Also, while the constitution of a display body using piezoelectric ink is disclosed in SID 98 Digest pp. 1131 to 1134, methods for disposing a large number of these display elements at a high density and methods for driving electrophoretic ink display elements disposed at a high density are not proposed.
The present invention was made in view of the abovementioned problems with the background art and it is an object of the present invention to realize piezoelectric transducers that can be easily miniaturized.
It is another object of the present invention to realize an electrophoretic ink display apparatus comprising electrophoretic ink display elements, a plurality of which are disposed at a high density.
The piezoelectric transducer relating to the present invention comprises a first electrode layer, a first piezoelectric film layer, a second electrode layer, a second piezoelectric film layer, and a third electrode layer, layered in that order on a substrate. The abovementioned first and second piezoelectric film layers are constrained so as not to expand or contract in a thickness direction.
With the abovementioned constitution, three-dimensional and planar miniaturization are possible because the piezoelectric transducer can be constituted by forming two piezoelectric film layers. Moreover, it becomes possible to realize a piezoelectric transducer that can withdraw a high load. Also, because the piezoelectric film layers are constrained so as not to expand or contract in a thickness direction, it becomes possible to realize a piezoelectric transducer with which direct voltage amplification is possible.
In the piezoelectric transducer relating to the present invention, a first electrode layer, a piezoelectric film layer, a second electrode layer, and third electrode layer are formed on a supporting base wherein a cavity is formed. The abovementioned second electrode layer and third electrode layer are formed in a pair, with an interval therebetween, on the piezoelectric film layer positioned above the abovementioned cavity.
With the abovementioned constitution, it is possible to form a miniaturized piezoelectric transducer.
The electrophoretic ink display apparatus relating to the present invention comprises a multiplicity of capsules. Comprising a plurality of electrophoretic ink display elements wherein the color changes with the movement of charged particles within the capsules, an electrophoretic ink display apparatus further comprises a plurality of gate lines, a plurality data lines intersecting with the gate lines, and thin film transistors disposed at the intersections of the abovementioned gate lines and data lines. One source-drain of the abovementioned thin film transistors is connected to the abovementioned data line; another source-drain of the abovementioned thin film transistors is connected to the input side of the piezoelectric transducer; and the output side of the abovementioned piezoelectric transducer is connected to the electrode of the electrophoretic ink display element.
The piezoelectric transducer relating to the present invention can be used as the abovementioned piezoelectric transducer. In that case, a columnar structure is established on the upper portion of the abovementioned piezoelectric transducer and the abovementioned columnar structure is pressed with the facing substrate on which the upper electrode of the abovementioned electrophoretic ink display element is established. The abovementioned first and second piezoelectric film layers can thereby be constrained so as not to expand or contract in a thickness direction.
With the abovementioned constitution, a multiplicity of disposed electrophoretic ink display elements can be driven with piezoelectric transducers while being addressed with thin film transistors.